Definition
A non probability sampling techniques that is a two stage restricted judgmental sampling. The first stage consists of developing control categories or quotas of population elements. In the second stag, sample elements are selected based on convenience or judgment.
Explanation
• It is a form of Non-Probability sampling.
• In Quota Sampling, the samples are selected in such a way that the interest parameters represented in the sample are in the same proportion as they are in the universe/ population.
• Quota Sampling is widely used in consumer panels.
• The following aspects must be kept in mind while choosing the control variables:
The variables must be available and should be recent.
They should be easy for the interviewer to classify.
They should be closely related to the variable being measured in the study.
The number of variable must be kept to a reasonable number so as to avoid confusion while analyzing the data
The cost of sample per unit is directly proportional to the number of control variables.
In order to have a check mechanism about the quality of samples taken so as to reduce the selection errors, Quota Samples are “validated” after they are taken.
The process of validation involves a comparison of the sample and the population with respect to characteristics not used as control variables. For e.g. in a quota sample taken from a consumer panel for which income, education, and age group are used as control variables. If the comparison of this panel and the population might be made with respect to such characteristics as average number of children, occupation of the chief wage earner and home ownership. Then if the panel differed significantly from the population with respect to any of these characteristics, it would be an indication of the potential bias in the selection procedures. It should be noted that the similarity does not necessarily mean the absence of bias.
Example
If one wants to select a Quota sample of persons for a test of flavored tea and wants to control (control variables are the parameters based on which he would like to classify the universe) it by ethnic background, income bracket, age group and geographical area. Then the sample taken would have the same proportion of people in each ethnic background, income bracket, age group and geographical area as the population.
Disadvantages
• Scope for high variances
• Scope for sizable selection errors.
• Selection errors arise from the way interviewers select the persons/ variables to fill the quota. Incorrect information of the proportions of the population in each of the control variables, biases in the relationship of the control variables to the variables being measured, and from other sources.
A non probability sampling techniques that is a two stage restricted judgmental sampling. The first stage consists of developing control categories or quotas of population elements. In the second stag, sample elements are selected based on convenience or judgment.
Explanation
• It is a form of Non-Probability sampling.
• In Quota Sampling, the samples are selected in such a way that the interest parameters represented in the sample are in the same proportion as they are in the universe/ population.
• Quota Sampling is widely used in consumer panels.
• The following aspects must be kept in mind while choosing the control variables:
The variables must be available and should be recent.
They should be easy for the interviewer to classify.
They should be closely related to the variable being measured in the study.
The number of variable must be kept to a reasonable number so as to avoid confusion while analyzing the data
The cost of sample per unit is directly proportional to the number of control variables.
In order to have a check mechanism about the quality of samples taken so as to reduce the selection errors, Quota Samples are “validated” after they are taken.
The process of validation involves a comparison of the sample and the population with respect to characteristics not used as control variables. For e.g. in a quota sample taken from a consumer panel for which income, education, and age group are used as control variables. If the comparison of this panel and the population might be made with respect to such characteristics as average number of children, occupation of the chief wage earner and home ownership. Then if the panel differed significantly from the population with respect to any of these characteristics, it would be an indication of the potential bias in the selection procedures. It should be noted that the similarity does not necessarily mean the absence of bias.
Example
If one wants to select a Quota sample of persons for a test of flavored tea and wants to control (control variables are the parameters based on which he would like to classify the universe) it by ethnic background, income bracket, age group and geographical area. Then the sample taken would have the same proportion of people in each ethnic background, income bracket, age group and geographical area as the population.
Disadvantages
• Scope for high variances
• Scope for sizable selection errors.
• Selection errors arise from the way interviewers select the persons/ variables to fill the quota. Incorrect information of the proportions of the population in each of the control variables, biases in the relationship of the control variables to the variables being measured, and from other sources.